Stereoscope.



L. c. D. A. GHRON.

STEREOSGOPB.

APPLICATION FILBD'OOT. 13, 1913.

I 1,1 14,232. Patented 0013.20, 1914.

3 SHEETS-SHEET l.

L.G.D.A.CHR0N. STBRBOSGOPE.

APPLIUATION FILED 00T.13, 1913.

1,1 14,232. l Patented 0ct.20,1914.

3 SHEETB--BHEET 2.

L. G. D. A. CHRON.

STBREOSCOPB.

APBLIOATION FILED 00T.13, 1913.

Patented 001.20, 1914.

3 SHEETS-SHEET 3.

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LOUIS CAMILLE DANIEL ANDR cH'RoN, or PARIS, FRANCE.

STEREOSCOPE.

Spccicaton of Letters Patent.

Patented Oct. 20, 1914,

Application `filed October 13, 1913. Serial No. 794,934.

T all 'zo/0772, t may concern.' y

Be it known that I, LoUIs CAMILLE DANIEL ANDR CHRON, a citizen of the Republic of France, and resident of Paris,

, France, have invented a certain new and useful Stereoscope,.which. is fully `set forth in the following specification.

This invention relates to apparatus `by means of which it is possible to magnify ordinary stereoscopic photographs, without the illusion of relief being in the least aii'ected. It is known.that for producing this relief impression, one condition is necessary which is that the right eye shall perceive the image formed by the right hand object glass, and only that image, and, conversely, that the left eye shall see only the image formed by the left-hand object glass, which condition is easilyV fulfilled in ordinary stereoscopes, owing to the presence of two eye-pieces which enable each eye to look only at the corresponding' 'image situated in the focal plane of the eye-pieces.

This invention. chiefly consists in enlarging the two pictures of a stereoscopic photograph or other object by projecting and, moreover, superpcsing them on a single condenser, in such a. manner that the rays coming from the right-hand picture, and the rays coming from the lett-hand picture, after havingintersected each other and continued their paths in accordance with their respective axes of proj cction, shall converge, the former only toward the right eye, and

' the latter only toward the left eye of the observer. Each eye thus sees only the real enlarged image of the corresponding picture, which is an essential condition for producing the illusion ofrelief. l

The apparatus vcomprises two main optical devices: the first one enables the images of the two pictures to be projected and at the same time enlarged vand. superposed (which result can be obtained in several ways, the chief among` which are hereinafter described by way of example), andthe second designed to make some of the rays forming the two superposcd images, converge toward the .right eve, and the others toward the lett eye ot the observer.

In the accompanying drawing 1-Il`igures l lto l are diagrammatic plan views showing various arrangements or' the said devices. Fig. is a vertical section of anl apparatus wherein such arrangementsmay be carried out. Fig.` 6 is a diagrammatic plan View of a still further arrangement.

In order to project and enlarge the two images by superposing them, as already stated, several arrangements may be followed, all of which employ two object glasses, (which can be ordinary achromatic lenses), corresponding each to one ofV thecomponent pictures I, I of a stereoscopic photograph or other object.

In the rst arrangement, (F ig. l), the object P is located in the'tocal plane of the object glasses O and 0, the axis of each of which glasses passes through the center of the corresponding picture. An achromatic lens L, of lsuilicient diameter to cover bothl glasses, is inserted in front of them, and the two images projected are then formed and superposed in the focal plane IPl of that lens. In fact the rays emitted by anytwo symmetrical points on the two pictures, are naturally caused by the object glasses to parallel each other, and these two parallel rays, after having passedV through the lens L, will naturally converge at one and the same peint in the focal plane of the said lens. It the focal length or' the single lens is twice or three times greater than that of the object glasses, the images projected will be formed at a distance from the lens which is twice or three times greater than that separating the object glasses from the object, and the enlargement will, therefore, be two or three diameters,that is to say, four or nine arcas. Naturally, in order to avoid useless bulk and weight, the large achromatic lens producing the superposition oI" the images can be cut in the shape of a rectangular rband of dimensions suiiicient simply to cover the two object glasses.

In the second arrangement, (F ig. 2), the object I) is arranged beyond the joint focal plane F of the two object glasses O', at the desired distance in order that, without interposition of any other lens, the projected images ofthe pictures I, I may be formed in the plane Il" at the other side of the two object glasses, which images will be two or three times larger, for instance, if it is desired to obtain enlargement of two or three diameters. But as it is necessary not only to project and magnify the images, but also to superpose them, Vas stated before, the object glasses are moved toward each other, so that the principal axis, instead of passing to a suiiicient extent in order that the superposition of the images projected shall take 4place'in the-said plane 11"., For instance,

if the magnifying obtained is of three diameters, the distance separating the object from the object glasses represents a quarter of the total distance separating the said object from'the plane of projection, and the shifting of centers of the object glasses relatively to each other will be a quarter. of the distance separating the centers of the images. l In the third arrangement (Fig. 8),' while thefprojecting andthe magnifying are still carried out as in the second arrangement, the superposition of the images in the projection plane can'vbe obtained by the simple interposition in front of each object glass o f a prism p p" of a suitable angle, the side faces 'of the prisms being arranged vertically and their bases turned toward-each other. But owing to dispersion, irisations on the outlines of the images will take place, unlessy `specia'lly-constructed prismsfare used.

When carrying o ut the projecting and the magnifying as the second arrange-` ment, the superposition of the. images could be vobtained by inelining the .two object .glasses toward each other, so thattheir axes a a instead of Vbeing parallel, yform an acute angle, as shown in Fig. 4, 1 This ,arranges ment is, moreover, equivalent to'a shifting of the centers ofthe object glasses relatively to each other, but `it'results, on the other hand, in afairly perceptible deformation of the limages.-The paths of the rays, Figs. 3

' ande, if extended, would be identically the same asin Figs. l and 2. 1; r Obviouslyfthe shifting of centers, interp'osition ofeagprism, or the inclination of the aijistceuldbe applied only to a single object glass-'instead of .toboth but the eX- tent'ofshifting the center o'r of theinclination of thefaXis, orl of the angle of the prism, must in such case be double thatv what it would be-whenboth object glasses have their centers shifted or are inclined or covered by a prism. Also the achromatic lens' (in they first ar-rangement), and the prisma, (in .the third arrangement) may-be situated behind,

instead of in front vof the object glasses.

Whatever be the arrangement employed,

I .it will be seenI that the first condition to be coming. from the right-hand image converge toward the right eye ofthe observer, andv those from `the left-hand image, toward his left eye. This 'device consists simply of a single condenserC, (Figs. 1 `and 2), preferably constituted by four or tiveplano-convexy images.

lpoint 'where the'imatge ,du

The second device is designedto full the -secondcondition, which is to make the rays llenses secured in a single' mount, the shape and dimensions of which must correspond to the'shape and dimensions of the two images 'superposed on the said condenser arranged exactly in the projection'p lane F of the said The whole of the four or five lenses of the condenser must havefsufh a focus that the object glasses should Ibe at one side at about double the said focal distance. Under these conditions, the condenseri'will .produce order to see withtheir full freliefthe two reall images,'z'. e., the pictures of the stereo-1' 'scopic photograph, magnified and superposed in the plane of the condenser. In fact,

the rays projected by the righthand object glass O, after having formed the right-hand image and intersected the rays forming the left-hand image at the plane of the condenser, are not ldeflected by the latter from their aXis of projection, but the condenser makes them -all converge to a point S on the said axis situated, (under the conditions hereinbefore assumed), at double its focus, and the said point representsexactly the image of the right-hand objectv lass.

The same is exactly true for the rays projected by` the left-hand object glass .O, which, atthe point` S', which point represents the image of the left-hand object glass.

It is sufficient that the vright eye of the observer should be in the field representedby the image of the lright-handv objectglass, and his left eye in the field represented by the limage of the left-hand object glass, in order that the two images ofthe photograph superposed in their plane of projec tion at the plane ofthecondenser, but seen each separately by the corresponding eye'of the observer, should produce the impression of stereoscopierelief. vIn order lto ,deter mine the positi'onior the eyes in an exact manner, an eye-piece can be xed at the of-eachv object glass S, S is formed an like-in lan ordinary stereoscope, the'lens of each eye-piece must tance separating the eye-piece from the image, that is to say, in the `present case from the condenser on which thetwo images have a focus approximately equalV to the'disare projected and superposed But as'the said distance is generally greater than' 25 cm., the lenses may be dispensed with, and

'i merely the cylindrical mounts of the eyepieces retained, intended simply to determine the position of the eyes. Nevertheless, this entire arrangement would be practically useless inthe formd'escribed, (that'isy to say if the stereoscopic photograph, the object glasses and the condenser were iny the LimenaA same horizontal plane), as the length ofthe apparatus would render it too cumbersome. In fact, even supposing that it is a question of photographstxlOZ mm., which are theymost usual ones and have the great advantage of requiring a photographic apparatus of very small dimensions, the apparatus employed to magnify the photographs 2H diameters would require 60-70 cm. It is, therefore, advisable to interpose inthe path of the rays one or more mirrors M M, (Fig. 5), so asto break up the said path, and to reduce to the same eX- tent the dimensions of the apparatus A. In order to avoid the double rellection and the formation of secondary images, itis preferable to use mirrors silver-platedy on theil outer surface. Moreover, it is possible to build an apparatus which could be adapted to ditferent types ofstereoscopes, vthe mechanical part thereof which is tended for the successive passage of the photographs in front of the eye-pieces can be retained,

and the few parts which have to be replacedv can be easily removed'or put on at will.

Fig. 5 is a diagrammatic view of the apparatus which appears to be the most practical and whichcan be easily adapted to a-ny classifying stereoscope of the usual type. The dotted lines show the upper portion of such a stereoscope T. A plate P carrying. theobjectglasses tits into a ground glass frame of the stereoscope. O is one of the object glasses utilized to project the image or" one of the pictures l of the ordinary stereoscopic. photograph, which is seen at the place which it normally occupies in the stereoscope. The two images are superposed at the plane or the said condenser owing to the achromatic lens L covering the two ebject glasses, (as in Fig. l). Of course, any

i oi. the other superposition arrangements hereinber'ore referred to, might be used-` ln the path of the rays, at M and M, are 111-. serted two mirrors inclined at. an angle of 90 relatively to each other, and both in-. I

clined at an angle of 45 tothe horizontal.

The rays, after having been reflected twice and formed the image at the plane of the vcondenser C, are concentrated by the latter at S `where is situated one ot the eye-pieces, (or one ol: the eye-piece mounts), secured by a rod to the 'cover of the stereoscope, or secured to the lighting apparatus which will be hereinafter described. The apparatus being represented in side elevation, it is impossible to show, as in the other figures, the second picture I `the second object glass Of and the second eye-piece S situated, respectively, in the same horizontal plane as the picture l, object glass O and the eyepiece' S. l

Of course, this device makes it necessary to light the object from the front,` instead of from the back of the stereoscope, where .ranged a small electric lamp, which are dittused by a ground glass in- .serted between the eye-pieces and the photograph. It is, howeverpreferable to cut a a length of at least.

the magnifying apparatus is'situated. The eye-pieces may be retained, andin front of cachot them, in a single casing, can be ari the rays of large shutter in the upper'I portion of the stereoscope door carrying the eye-pieces, and to replace it by a ground glass D, in front of which will be arranged one or two electric bulbs X provided with a reflector Z; the said ground'glass might, however, be arranged in any. other suitable position, namely close tothe photograph. y

As already stated, the right eye must see only the right-hand image, and the left eye only the left-hand image. As the images are superposed, and'asthe rays intersect at the plane of the condenser, each eye would .see the opposite image, if the photographic pictures constituting the object were left, gelatin slide in front, in their `grooved frames, as in an 'ordinary stereoscope. It is, therefore, necessary to place the photograph with the gelatin side backward, (that is to sai/,the gelatin facing the magnifying apparatus), in order `that each eye shall see the image intended for it. But in any case it is not necessary to turn the photograph upside down, for if each image is turned over in the horizontal direction, ow-y ing to its projection through an object glass, it is straightened in the vertical direction owing to its double reflection on the mirrors arranged .at-an angle of 900. Fi-

nally, if it is desired to take advantage oit Y the device which, -in certain classifying stereoscopes, makes it possible to read an inscription on the gelatin side between the two `pictures of the -photograph,.it is necessary to turn such device over and to place it behind the photograph projected, that is to say, between the latter and the object glasses of the magnifying apparatus.

In the preceding description, there has been mention vonly of magnifying photographs of a size l5 :t l0? mm., because it is the most lusual stereoscopic size and,`(be ing also the smallest), benefits to the greatest extent Yby the magnifying of. the images, but it is needless to' add that everything that has-been said with reference to that size, is equally well applicable to any other stereoscopic size. Moreover, instead of being itted to a Classif ing stereoscope, the price of which is always high, the apparatus l described might also'be fitted to an ordinary stereoscope in which the objects are introduced by hand into a groove provided for the purpose. A system of lighting'will. however, always be indispensable'and, more` over, the weight and the dimensions of the magnifying apparatus `combined with stereoscope, no matter how small, will always necessitate the use of 'a leg or some support. Moreover, the mirrors, instead of being arranged as described, might be com- .bined in'some other way, forinstance so, as

tobreak the rays, in passing, into the shape -ordinary stereoscope. The objects remain fixed in their respective positions, and the eyes cease to see the limage as soon as they leave the field of the eye-pieces. Nevertheless, the apparatus described is also suitable for examining photographs made with a special-"apparatus taking more than two pictures of the same object in a single exposure vand on` one plate. `These photographs, examinedv with the above mentioned apparatus, not only show the stereoscopic relief, but also the-shifting of the objects relatively to each other, as the eyes are being vvmoved in a horizontal line, at least within certain limits.

Let it be assumed that the stereoscopic photograph .or object comprises four pictures I I I", 1 'arranofedy side b side v 7 3 3 ZD y 7 (Fig. 6)-, these four pictures representin -the four different aspects of the object. y seen from four different. points.

This photograph or object is placed into a magnifyingstereoseope similar to that hereinbefore described, in which the two object glasses `are replaced by four object glasses D, D,

D, D (Fig. 6), the axes of which must correspond to the centers of the pictures and which can be simple achromatic lenses. Theseobj ect glasses must be' cut as shown in Fig. 6 so as to be tangent along lines, and

not along simple points. A' single achromatic lens L covering the four object glasses,

projects and superposes the images ofthe four pictures into its focal plane inwhich is arranged the condenser C. The latter causes the rays to converge to a plane where are formed the images arranged side by side of the four" object glasses representing four zones in which the eyes, in moving horizontally, will see the object S in four different aspects that it wouldfhave if viewed successively from the four points. (In order not to complicate the figure, the path of the rays have not been shown beyond the condenser C, and no account has .been

' taken of the reflection due to mirrors).

Assuming that the size of L1=5xl07 mm. is retained, the apparatus will comprise, for instance, four small rectangular cells each 25 mm. wide b5, about 35 high, to which will correspond four object glasses of identical focus, provided with a joint shutter.

The photographic plate,'in a frame, will be arranged in the focal plane, and't'will present, after development, four images arranged side by side in the direction of length, each 25x35 mm,

In the magnifying formingvthe object "glass must be cut to 25 mm., so as to be tangent by lines, andso as to correspond exactly to the four images 'stereoscope, the lenses which they willproject on the condenser. The large achromatic, lens covering the four object glasses must, therefore, be at least 10 cm. in diameter, and it could, of course, Abe

cut in the shape ofa rectangular band covering the object glasses, although other sizes and other dimensions could -be adopted, as, for instance, those adopted for ordinary stereoscopic photographs. Moreover, vthe r number of imagesof each photograph and, consequently, the "number of cells ofthe apparatus and the number of corresponding object glasses, could be'reduced to three or increased to a larger number.

I claims- 1. In a magnifying stereoscope, the combination'of an optical device for projecting, magnifying and superposing the images of the two component pictures of a stereoscopic photograph; and an opticaldevicefor causing'the rays coming from the right-hand image to converge towardl the right eye, and those coming from the left-hand' image toward the left eye of the observer.

2. In a magnifying stereoscope, bination of two object glasses for projecting and superposing the images ofthe two com ponent pictures `of a stereoscopic photo` the comgraph placed in the joint focal lane ofsaid glasses, the axisof each g ass passing through the center of the corresponding picture; an achromatic lens of suflicient diameter to cover the two object glasses inserted adjacent the same; and an optical device' for-causing the rays coming from the right-hand image, to converge -toward the right eye, and those coming from the left hand image toward the left eye of the observer. v

3. In a magnifying stereoscope, the combination of two object glasses' for projecting and. superposing the images of the two component pictures of a stereoscopic photo.

graph arranged in the joint focal plane 'of said glasses, 'the axis of each glass passing through the center of the corresponding image, an achromatic lens of sufficient diameter to cover the two object glasses inserted in front thereof;` and al single condenser arranged in the planev of projection of the images and constituted by plano-con- Vex lenses arranged 'back to back and secured in a single mount. 'f I 4. In a magnifying stereoscope, the combination of an optical device for projecting, magnifying and superposing the images of the two component pictures of a stereoscopic :'1- ihotovra h' an o tical device for causinor b 7 C the rays coming from' the right-hand image to converge toward the right eye, and those coming from the left-hand image toward the left eye ofthe observer; and asystem of f, mirrors inserted between said optical devices to break up the path of the rays and reduce the length and the bulk of the apparatus. 5. In a magnifying stereoscope, the combination of an optical device for projecting,

.:: magnifying and superposing the images of the two component pictures of a stereoscopic 4 photograph; an optical device for causing the rays coming from the right-hand image to convergetoward the right eye, and those coming from the left-hand image toward the left eye of the observer; a system of mirrors inserted between the said optical devices to break up the path of the rays and reduce the length and bulk of the apparatus; and a system of lighting vfor the stereoscopic photographs.

6. In a magnifying stereoscope, the combination of an optical ldevice for projecting, magnifying and superposing the images of vthe two component pictures of a stereoscopic 'l length and bulk of the apparatus; a system of lighting for the stereoscopic photographs; and a system of eye-pieces for viewing the vfinal `magnified and superposed 1mages.

7. In a magnifying stereoscope, the combination of an optical device for projecting,

magnifying and superposing the images. of

the plurality of component pictures of. a stereoscopic photograph; and an optical de` .vice for causing some ofthe rays forming the superposed images toward a plurality of points of observation.

In testimony whereof I 'have signed this specification in the presence of two subscribing witnesses.

LOUISKOAMILLE DANIEL ANDR CHRON.

Witnesses: l EimLY LEDRET,

HANsoN C. COXE. 

